Prior systems for setting whipstocks have employed wireline-set packers, which generally require specialized equipment at the surface to properly position the packer in the wellbore. Thereafter, an electric signal is sent from the surface to the packer to initiate a reaction which creates pressure which, in turn, creates relative movement to set the packer and release therefrom. These systems involve multiple trips into the wellbore with such packers as the Baker Hughes model DW-1, which was an electric wireline-set packer. Generally, these packers have orienting keyways and various survey subs would be run into the wellbore with the packer to obtain the necessary readings on the orientation of the keyway within the packer. Subsequently on a separate run, the whipstock would be installed into the packer after the setting tool was removed with the wireline.
Because electric line-set packers required the running of the electric line to the packer, it was not possible with that design to run the packer and whipstock into the well in one trip.
In some instances, the portion of the wellbore below the packer would also continue to be in service, meaning that not only would there be production through the newly created deviated wellbore but production would also continue through the newly set packer which had supported the whipstock. In known hydraulically set designs, portions of the setting mechanism, such as setting pistons and seals, were integral to the packer. These seals presented potential leakpaths from the annulus to the tubing later mounted to the packer should such seals fail.
Various techniques for positioning and orienting whipstocks have been developed, such as illustrated in U.S. Pat. No. 5,341,873. One-trip milling techniques when using a whipstock are illustrated in U.S. Pat. No. 5,109,924.
Other systems have proclaimed to be one-trip systems but, in fact, have required multiple trips to mill a window to create a deviation in an existing wellbore. The systems developed by A-Z Grant International for casing sidetrack systems, under a system called "Pack-Stock.RTM." and "Anchor Stock" have claimed to be a one-trip system but have, in fact, required the whipstock to be run in with a starter mill. Subsequently, another trip into the well was necessary to replace the starter mill to finish the milling operation. This system also did not address the issue of the leakpaths in the packer if the setting mechanism, whether located above or below the packer, is left in the wellbore upon removal of the whipstock. The Z-S system required a specially designed packer and did not provide for release of the whipstock and setting tool from the packer. This system could not use a standard wireline-set packer in a one-trip system. The principal problems of past systems were that either a two-trip system was required to avoid the leakpath problem by using a wireline, or a multiple-trip system was required that left various setting pistons and their seals in the packer body for potential tubing/annulus leakpaths.
Accordingly, it is an object of the present invention to provide a one-trip system, with the additional benefits that upon removal of the whipstock, the setting mechanism for the packer is removed, thereby eliminating potential annulus-to-tubing leakpaths in prior design packers. Additionally, wireline-set packers can be run with the apparatus and method of the present invention without need of a wireline rig. A single window-cutting mill can also be employed as one of the objects of the invention so that upon setting of the packer, the milling can begin on the same trip until the window is finished. The whipstock can then be retrieved with a variety of retrieving tools in a manner that will bring out the setting tool for the packer.